There have been proposed a number of antibacterial filaments comprising synthetic filaments, such as polyamide filaments including nylon 6, which contain powder materials having antibacterial properties.
Of the powder materials having antibacterial properties, silver-based inorganic antibacterial agents, in particular, phosphate antibacterial agents carrying silver ions, zeolite antibacterial agents carrying silver ions and calcined hydroxyapatite antibacterial agents carrying silver ions have been widely in use.
The filaments containing such silver-based inorganic antibacterial agents have good antibacterial properties and excellent durability. They, however, undergo color changes (color development) when subjected to treatment with an alkaline solution so as to scour sizing agents, which has been provided to improve weaving properties, away in the step prior to dyeing operation because the silver as an antibacterial component is oxidized by the treatment, what is worse, their antibacterial properties deteriorate. Thus silver inorganic antibacterial agents have disadvantages in that they are not suitably used in applications where treatment with an alkaline solution is carried out.
In order to prevent color change in filaments and to improve the whiteness of the same, there have been proposed antibacterial filaments having been treated with color-change preventing agents, such as sodium percarbonate, sodium hypochlorite or azole compounds having no mercapt group, in JP-A-4-50376, JP-A-6-264360 and JP-A-6-272173. These filaments, though they have been treated with color-change preventing agents, still have the problems in that they are unable to satisfactorily avoid color change (color development) caused by treatment with an alkaline solution, the treatment is complicated, and that they are hard to use in applications, such as clothing applications, where whiteness is required.